Metallic coating exit machine with driven rolls



Jan. 9, 1962' K. OGANOWSKI ETAL 3,016,041

METALLIC COATING EXIT MACHINE WITH DRIVEN ROLLS Filed May 13, 195'? ilk... a

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atent Patented Jan. 9, 1962 fiice 3,016,041 METALLIC COATING EXIT MACHINE WITH DRIVEN ROLLS Kasimir (Eganowsiri, West Middletown, and Forrest M. Morrow, Middietown, Ohio, assignors to Armco Steel Corporation, hiiddletown, Ohio, a corporation of Ohio Filed May 13, 1957, Ser. .NO. 653,742 4 Claims. (Cl. 118419) This invention has to do with an exit machine with driven rolls used in a metallic coating apparatus. It is conventional in metal coating practice to control the weight of the coating and the uniformity thereof. Thus, for example, in the hot dip coating of steel sheets and strip the coating weight and the uniformity is controlled by means of exit rolls which are vertically adjustable so that the weight of coating is controlled principally by the vertical position of the rolls with respect to the surface of the coating bath. The uniformity of the coating is controlled by horizontal alignment of the rolls and uniform pressure between them.

In the coating of sheets the exit rolls are usually power driven because they have a function in propelling the sheets through the coating bath. In the coating of strip, however, the exit rolls can be driven by the friction between the strip and the roll surfaces, if the strip driving torque is greater than the braking torque resulting from hearing friction and from wipers and other mechanisms which are required for the proper positioning and operation of the rolls.

It has been found that in certain gauges and with certain speeds a strip friction drive may be inadequate for complete control of the coating within the desired range of coating Weights. In such cases it may be desirable to apply an external drive to the rolls so that rotation of the rolls at a uniform speed is assured under all operating conditions. Such conditions may require the peripheral speed of the rolls to be equal to strip speed or to be either greater or less than strip speed.

Presently used exit machines which provide for driven exit rolls do not however provide for the uniform rotation of the rolls and for uniform pressure between the rolls and as a result such machines do not provide the desired uniformity of coating. When driven rolls are used, two driving torques are applied to the rolls. One is the torque resulting from the friction between the strip and the rolls and the other torque is that imposed by the external drive. The sum of these torques must overcome the sum of all braking torques resulting from the roll-supporting, wiping and adjusting mechanisms.

Since the rolls generally operate at least partially submerged in the molten metal they are in contact with surface scum in the coating bath and since the rolls and all related mechanisms are subject to corrosion and erosion by the molten metal, the frictional eifects and braking torques will vary over a considerable range. Such variations present a serious problem under conditions where it is required that the exit rolls operate at a peripheral speed which is less than strip speed. Frequently the braking torques at the lower values will fall below the driving torque resulting from the friction between the strip and the roll. Under such conditions the roll has a tendency to assume the speed of the strip and the external drive must impose a braking torque in order to maintain the slower peripheral speed of the roll. Because of the inherent looseness in the connections between the drive for the exit rolls and the exit rolls, an unavoidable backlash occurs during the change of direction of the torque. A momentary change in the speed of the roll or a momentary stoppage of the roll impairs the uniformity and appearance of the coating.

In addition to the fluctuation of the driving torque and the braking torque as discussed above the fact that in presently used coating apparatus inadequate provision is made to maintain a constant pressure between the rolls further complicates the problem. In presently used pressure controlling mechanism the working parts are partially or totally submerged in the molten metal. As a result of wear and corrosion the moving and supporting parts seat themselves and lose their responsiveness to pressure adjustment. Attempts to force the rolls into the desired position require the exertion of a considerable pressure and this results in misalignment of the rolls and loss of uniformity of the coating.

With the foregoing considerations in mind it is an ob ject of the present invention to provide an apparatus which overcomes the various difiiculties described above. It is an object of the present invention to provide an ap paratus wherein each of the exit rolls is provided with independent braking means. It is another object of the invention to provide an apparatus as outlined above wherein means are provided to yieldingly and adjustably urge one roll of a pair of exit rolls toward the other so as to maintain a desired constant pressure between them. It is still another object of the invention to provide an adjusting means which is disposed above the level of molten metal in the coating bath so that the working parts will not be subject to corrosion or erosion and will continue to function accurately.

These and other objects of the invention which will be described in greater detail hereinafter or which will become apparent to one skilled in the art upon reading these specification we accomplish by that construction and arrangement of parts of which we shall now show an exemplary embodiment.

Reference is made to the drawings forming a part hereof and in which FIGURE 1 is an elevational view of an exit machine according to the invention.

FIGURE 2 is an elevational view of the same as seen from the right of FIGURE 1.

FIGURE 3 is a diagrammatic view showing the location of the exit rolls with reference to the rip being coated and the molten coating metal bath.

FIGURE 4 is a fragmentary cross-sectional view taken on the line 4-4 of FIGURE 1.

Briefly, in the practice of the invention we mount one of the exit rolls between a pair of frame elements which provide bearings for the rolls. We mount the other roll of the pair in an auxiliary pair of frame members which are pivotally secured to the first mentioned frame members. On each of the frame members we mount braking means for the respective rolls and we provide means whereby the pivotally mounted members may be urged in a direction to force the rolls together.

Referring now in more detail to the drawings, we have shown a pair of exit rolls at It} and 11. These rolls are driven by conventional driving means (not shown) through the coupling means 11b. As best seen in FIG- URE 3, the rolls are generally partially submerged in the molten coating metal bath 1'2 and the strip being coated passes out of the bath between the rolls 1%) and 11 and is indicated at 13. The rolls 1% and 11 may be provided with roll necks 10a and 11a. The roll It? is mounted between a pair of frame members 14 provided with the recesses 15 in which are provided the bearing blocks 15 which are engaged by the roll necks liia. A pair of supplemental frame members are provided at 17 and these are pivoted as at 13 by means of bolts or the like from brackets 19 which are secured to the members 14a. It will be understod that the members 17 may thus be pivoted with respect to the members 14a about the pivot point 18. The members 17 may be held on the bolts 18 by means of collars 20 provided with set screws as shown in FIGURE 4. The members Eda are removably secured to the members 14 by the eye-bolts 50 engaging pins 51 on the member 14, and secured by nuts 52 engaging an abutment 53 on the member 14a.

'The members 17 have the recesses 21 in which are disposed the bearing blocks 22 which form bearings for the roll necks 11a.

The braking means for the various rolls are identical and we shall describe the braking means for the roll it? as seen at the left of FIGURE 1. This braking means comprises a pair of levers 23-2 pivoted together at 25 in scissors relationship, the pivot bolt or the like being firmly attached to frame member 14. The lower ends of the levers 23' and 24 are provided with the brake shoes 23a and 24a which are in engagement with the roll neck 16a. The upper ends of the levers are connected by a pin 25 which is secured to the lever 24 by the nuts 27 and which passes through the end of the lever 23. A spring 23 is confined between the end of the lever 23 and a washer 29 held in position by a nut 312'.

It will be clear that the spring 28 will tend to close the scissors or urge the upper end of the lever 23 toward the upper end of the lever 24. This of course results in pressing the brake shoes 23a and 2% against the roll neck a. The pressure with which the brake shoes engage the roll neck is of course adjustable by means of the nut 30.

It will be understood that a similar mechanism may be provided at the other end of the roll it} and a similar mechanism at each end of the roll 11. It will also be clear that the braking may be carried out on the surface of the roll itself beyond where it engages the strip being coated or a brake disc or drum may be provided especially for the purpose within the scope of the present invention, either in or out of contact with the molten zinc.

To urge the roll 11 toward the roll 10 We provide the levers 31 which are pivoted to the member 14a as at 32. The lower ends of the levers 3ft bear against lugs 33 formed in the members 17 so that if the levers 31 are rocked in a clockwise direction, as seen in FIGURE 1, the blocks 17 will be swung in a clockwise direction urging the roll 11 against the roll 10.

The upper ends of the levers 31 are provided with the yokes 34 which carry the nuts 35 in a pivotal manner pivoting about the point 36. The nuts 35 engage threads 37 on the rods 38 which are provided with the cranks 39. A spring 40 mountedin a spring housing 41 secured to the block 14 bears on a block 42 in which the rod 38 is seated. It will be clear that the spring 40 urges the rod 38 axially toward the right and that this tends to produce a clockwise rocking of the lever 31. The pressure exerted by the spring can be adjusted by rotation of the crank' 39 to move the nut 35 axially along the rod 38.

It will be understood that there is a lever 31 on each side of the apparatus and that the adjusting mechanism associated with the lever 31 is repeated on the other side of the apparatus as seen in FIGURE 2.

It will be clear from a consideration of the figure that the mechanisms including the spring 40, the crank 39, the screw 37, the pivot point 32 and the pivot point 18 are all above the surface of the molten metal coating bath and these parts are therefore not subject to corrosion or erosion as outlined at the outset. The adjusting portions and springs of the scissors mechanisms are also above the level of the bath so that these are not subject to malfunction by reason of corrosion.

It will be understood that if desired the braking mechanisms could be disposed on the outside of the coating bath and the brakes could act upon shaft extensions outside the coating pot. It will also be clear that numerous other modifications may be made without departing from the spirit of our invention. We therefore do not intend to limit ourselves otherwise than as set forth in the claims which follow.

Having now fully described our invention, what we claim as new and desire to protect by Letters Patent is:

1. In an apparatus for producing a metallic coating on a metal strip, said apparatus having a pair of driven exit rolls, means for yieldingly and adjustably urging one roll of said pair toward the other, and means independentof said urging means for applying an individual direct acting braking efiort to each roll of said pair.

2. A structure according to claim 1, wherein the yielding and adjustable means are disposed above said exit rolls. V 3. In an apparatus for producing a metallic coating on a metal strip, said apparatus having a pair of driven exit rolls, rigid mounting means providing bearings for one roll of said pair, means providing bearings for the other roll of said pair, said last mentioned means being pivotally mounted with respect to said first mentioned means, means for yieldingly and adjustably rocking said pivotally mounted means with respect to said first mentioned means to urge the roll carried thereby toward the-other roll, and means independent of said rocking means for applying an individual, direct acting braking effort to each roll of said pair, one of 'said braking effort applying means being mounted on said rigid mounting means and the other of said braking effort applying means being mounted on said pivotally mounted means.

4. A structure according to claim 3, wherein the yielding and adjustable means are disposed above said exit rolls.

References Cited in the file of this patent UNITED STATES PATENTS 1,442,838 West Jan. 23, 1923 1,641,978 Lundquist Sept. 13, 1927 1,650,442 Goldstein Nov. 22, 1927 2,236,213 Jenkins et al Mar. 25, 1941 2,245,303 Shane June 10, 1941 2,742,019 Queer Apr. 17, 1956 

